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In human physiology, the atria facilitate circulation primarily by allowing uninterrupted venous flow to the heart during ventricular systole. [22] [23] By being partially empty and distensible, atria prevent the interruption of venous flow to the heart that would occur during ventricular systole if the veins ended at the inlet valves of the ...
Venous return (VR) is the flow of blood back to the heart. Under steady-state conditions, venous return must equal cardiac output (Q), when averaged over time because the cardiovascular system is essentially a closed loop. Otherwise, blood would accumulate in either the systemic or pulmonary circulations.
Its posterior wall is formed by the ventricular septum, which bulges into the right ventricle, so that a transverse section of the cavity presents a semilunar outline. Its upper and left angle forms a conical pouch, the conus arteriosus , from which the pulmonary artery arises.
Layers of vein wall shown in comparison to arterial wall. There are three sizes of vein, large, medium, and small. Smaller veins are called venules. The smallest veins are the post-capillary venules. Veins have a similar three-layered structure to arteries. The layers known as tunicae have a concentric arrangement that forms the wall of the vessel.
Respiratory pump - Intrapleural pressure decreases during inspiration and abdominal pressure increases, squeezing local abdominal veins, allowing thoracic veins to expand and increase blood flow towards the right atrium. Skeletal muscle pump - In the deep veins of the legs, surrounding muscles squeeze veins and pump blood back towards the heart ...
The anatomy of the veins of the heart is very variable, but generally it is formed by the following veins: heart veins that go into the coronary sinus: the great cardiac vein, the middle cardiac vein, the small cardiac vein, the posterior vein of the left ventricle, and the oblique vein of Marshall.
The smallest cardiac veins (also known as the Thebesian veins (named for Adam Christian Thebesius) are small, valveless veins in the walls of all four heart chambers [1] that drain venous blood from the myocardium [2] directly into any of the heart chambers. [3] They are most abundant in the right atrium, and least abundant in the left ventricle.
Posterior vein of left ventricle (accompanies the left marginal artery, ascends the posterior wall of left ventricle to drain into the coronary sinus); [6] Oblique vein of left atrium. [1] All veins that empty into the coronary sinus except for the oblique vein of the left atrium have valves at their junction with the coronary sinus. [1]